refactor: remove old hack to get around winwidth

This was put in place when I was using winwidth to resize my windows,
but didn't want it to cause aerial window to resize. I've changed my
thinking since then. I personally think that winwidth should be ignored
in winfixwidth windows, but vim does not agree. Since it isn't, aerial
should _not_ perform any surprising operations (particularly ones like
this, with side effects) to break the default behavior.

lua/aerial/autocommands.lua

@@ -96,9 +96,6 @@ M.on_enter_buffer = util.throttle(function()
       or vim.tbl_count(vim.api.nvim_tabpage_list_wins(0)) == 1
     then
       vim.cmd("quit")
-    else
-      -- Hack to ignore winwidth
-      util.restore_width(0, 0)
     end
     return
   end